The present invention relates to devices utilizing sequentially or serially activated power switches and more particularly to electronic means for accomplishing such switching in a predetermined time sequence.
Devices in accordance with the present invention find application in sequential activation of various devices on a regular basis to define a cycle of fixed time period where the cycle is automatically repeated until intentionally interrupted.
Devices in accordance with the present invention are particularly useful in activation and deactivation of signs of various description. One known class of prior art devised for such purposes, which are well known in the art have generally been of the electromechanical type where a mechanically driven arm or wiper is driven to sequentially open and close sets of electrical contacts to activate and deactivate associated power circuits, for example to turn on or turn off a number of lights of a sign.
It will be recognized that such devises have inherent disadvantages. For example, the mechanical drive for the contactor or wiper arm is susceptible to problems normally associated with mechanical devices such as breakage, or slippage where the connection between the arm of the drive malfunctions or misalignment where the wiper arm does not close the contact either as a result of wear of the contacts or wear of the arm.
In any event, such devices require significant maintenance for continued regular operation and, because of the complex electromechanical drive mechanisms needed for reliable operation, such prior art devices have been expensive to fabricate and in some cases the cost of fabrication precludes the utilization of such devices.
Moreover, such prior electromechanical devices have been expensive to fabricate because of the mechancial devices and, also because of the mechanical devices, have not been susceptible to miniaturization. Consequently such devices have not been available for use in miniature form, for example in model layout applications.